Gaze into the night sky and look at our Moon, our unique celestial companion. As we all know, through-out the year, our Moon appears to vary in size, although of course it's size is constant. The reason for this apparent variation is that the moon, of course, does not produce any light, it merely reflects light from the sun and, as such, can be seen both during the day and night, or sometimes not at all.

The reason for this is that we see the moon in phases. To understand these phases it needs to be remembered that the earth orbits the sun in about 365 days and the earth rotates on its axis a full circle in about 24 hours with the moon orbiting the earth. The moon takes about 28 days to orbit the entire planet of earth. The position of the earth, sun or moon affects the phases of the moon and which part of the moon we can see.

This free online moon phases calendar and calculator will identify, in real time, how the moon is seen here on Earth. The image above in our moon phases calendar will show you exactly what part of the Moon can be seen right now, if at all. The moon phases calendar is divided into 4 parts: new moon (where you see no moon at all), first quarter (only half of the moon can be seen), third quarter (only half of the moon can be seen), and full moon (the entire moon can be seen). Our free online moon phases calendar will help clarify your understanding of how we seen the moon.